Multifunctional Integrated Organic–Inorganic-Metal Hybrid Aerogel for Excellent Thermal Insulation and Electromagnetic Shielding Performance

Highlights The homogeneous hybridization of organic–inorganic-metal elements in 3D aerogel was achieved by an expeditious method. The aerogel tightly integrates excellent thermal insulation (49.6 mW m−1 K−1), ablative resistance, mechanical strength, and superhydrophobic properties. The ablated carbon aerogel combines notable electromagnetic interference shielding properties (31.6 dB) and load-carrying properties (272.8 kN·m kg−1). Supplementary Information The online version contains supplementary material available at 10.1007/s40820-024-01409-1.

Thermal stability properties.The TGA was carried out from the ambient temperature to 1000 °C using TA instruments (TGAQ50) at 20 °C/min under N2.The TG-IR analysis was performed on the ThermoFisher (is50) and NETZSCH (STA449F3) under Ar atmosphere at the heating rate of 10 °C/min from 30 to 1000 °C, and the FT-IR resolution is 4 cm -1 .
Thermal insulation properties.Thermal conductivity (λ) and thermal diffusion (α) values of the aerogels were acquired through thermal constant analyze equipment Hot Disk (TPS2200), with the atmospheric pressure under the room temperature and a heating power of 5 mW for 10 s.The thermal images were recorded by a thermal infrared imager Guide sensmart (PS610).The ablative insulating behaviors were tested on a butane flame torch system for 60 s.

Finite Element Analysis of Ablation
Behavior.The ablation model was calculated using the COMSOL Multiphysics software.The thermal response of the aerogel can be solved using the partial differential equation (PDE) established by the system.A 2D axisymmetric geometry model is created with dimensions φ30×10 mm 3 , ablation time 60s, the natural cooling 40s, and the ablation temperature 1300 °C.The boundary conditions including heat flux and gas pressure are shown in Fig. S1.For heat flux, the surface boundary of the model is set to "Neumann boundary conditions" for calculating the surface energy changes, while the other boundaries are set to convective dissipation.The initial temperature is set to 303.15 K.For gas pressures, all boundaries are set to "Dirichlet boundary conditions" with an initial static pressure of 1 atm.The domain probe was inserted to output the temperature change parameter of the point with time to achieve the solution of the back temperature.The fully coupled transient solver is used for numerical calculation of the ablation model.Electromagnetic Measurements.The EMI shielding performance of the samples was measured by a vector network analyzer (Anritsu, MS4644A) based on the wave-guide method in X-band (22.86 mm×10.16mm).
Electrical conductivity.The electrical conductivities of the samples ablated at 800, 1000, 1200, 1400 and 1600 °C were obtained by four-point probing system (Guangzhou Four Probes, RTS-8).The electrical conductivity of samples ablated at 600 °C was tested by ultra-high resistance micro current insulation surface resistivity tester (Suzhou JingGe, ST2643).The conduction path diagram of LED lamp powered by electrochemical workstation with voltage of 1.5 V (CHI760E).

S2 Supplementary Figures and Tables
Chemical

Superhydrophobic properties
Hydrophobicity is also a key requirement for aerogels to be used outdoors [1].The static water contact Angle (SCA) of aerogels with different tantalum content is greater than 150°, which indicates super-hydrophobicity, as shown in Fig. S5.When BSiTa0.2-PA is immersed in water by an external force, the presence of an air cushion between the water and the aerogel results in reflectivity or a large number of microbubbles on the aerogel surface (Fig. S6a-left).This phenomenon indicates that the water is in the Cassie-Baxter state, and the interaction between the water and the aerogel is very weak.When different aqueous solutions (such as milk, orange juice, dye solution, sodium chloride solution, coffee and tea) are dropped on the surface of BSiTa0.2-PA, the droplets stand stably on the aerogel in an almost spherical shape (Fig. S6aright), and the SCA of these contaminative solutions is greater than 150°, as shown in Fig. S6b.This indicates that BSiTa0.2-PAhas broad-spectrum anti-pollution performance.The hydrophobicity of BSiTa-PA can be attributed to the following aspects: (1) The hydrophobic aromatic skeleton structure of the hybrid phenolic resin is stably chelated with the hydrolyzed product of tantalum precursor, resulting in a very low surface energy of the aerogel; (2) The multi-scale micro-nano structure of BSiTa-PA constructs the rough surface (Fig. 2j).

Model of SAXS fitting
For SAXS measurements, powder samples were held in place by two tape sheets, in which an empty cavity with two tape sheets was measured as a blank for the sample holder scattering signal.The scattering from the sample holder, when used, has been subtracted.The SAXS patterns were shown in log-log scale.
According to the theoretical models proposed by Saurel et al. [2], the SAXS signal in a range from 0.01 to 1.00 Å -1 of microporous carbon powders is mainly contributed by two components: (i) a scattering signal IPorod at a low Q range based on Porod's law (Eq.S1), ascribed to the macroscopic surface are of the powder grains; (ii) a signal Imp in the intermediate Q range caused by microporosity whose profile depends on its nature (Eq.S2).
where n is the Porod's final slope.A slope of -4 represents a smooth interface between domains in a multiphase system, while slopes between -3 and -4 characterize rough interface.In this work, the slopes are in the range from -3.6 to -3.9.
where a, C1 and C2 are adjustable parameters.C1 and C2 can be extracted from the refinement fitting results to calculate the average pore-pore distance (d) and amphiphilic factor (fa) considered as a disorder parameter as defined in the following Eqs.S3 and S4: ) The average pore radius r can be estimated by analogy with the globulus form factor defined in Eq.S5: The SAXS fitting results listed as below.

Comparisons of performances
Comparison with other types of high-performance aerogels is shown in Table S4.The preparation efficiency of BSiTa-PA developed in this work is significantly higher and the preparation cost is lower, which is very conducive to the further application development.Moreover, BSiTa-PA possesses significant advantages in thermal stability and shapemaintaining ability, which provides an important guarantee for the improvement of its ablative resistance and electromagnetic shielding performance.

Fig. S1
Fig. S1 The boundary condition of heat flux Contact angles measurements.Water contact angles (WCA) were measured and calculated using a contact angle analyzer (Dataphysics OCA-15EC, Germany) using 2 μL water droplets.Compression properties.Compression tests were measured on blocks by the universal test machine (SANS, CMT6303) with a displacement rate of 1 mm/min.

Fig. S5
Fig. S5 Static water contact angles of different aerogels

Fig. S11
Fig. S11 The fitting results of SAXS (d: pore-pore distance; fa: disorder parameter; r: average pore radius) SEM, EDS and SCA of ablated aerogels

Table S1
The fitting parameters (C1 and C2), and calculated d, fa and r values for BSiTa0.2-PAsamples at pyrolysis temperature from 800 to 1600 ℃

Table S2
Density, pore size and mechanical characteristics of BSi-PA and BSiTa-PA

Table S5
Comparisons of performances of BSiTa-PA with other high-performance aerogels